Millions of children have gazed up at the massive blue whale model in the Natural History Museum in London and wondered at the sheer size of the largest animal to have lived. Now scientists believe that they have discovered why whales became so big.
Blue whales can grow to 30m (100ft), the length of a Boeing 737 airliner, but such size is a relatively recent feature in their evolutionary history.
Thirty million years ago, similar filter-feeding whales were much smaller, typically a maximum of 10m long. Very large whales began appearing only about two to three million years ago, according to a study of fossil whale skulls by the Smithsonian National Museum of Natural History in Washington DC.
Researchers found that the increase in size